The invention relates to the MOCVD of barrier metal thin films, more specifically for use in connection with CVD copper interconnects.
Diffusion barriers are commonly used in integrated circuit (IC) fabrication to prevent interdiffusion of metals. For example, a TiN film is used to prevent diffusion of Al into Si at contact regions and along metal lines. As the dimensions of ICs, particularly contact regions and metal lines, continue to shrink, the requirements for the conducting barrier also become more stringent. Thinner barriers are required without substantially increasing resistivity. Barriers also need to be more resistant to diffusion of various new metals, which are being introduced into production processes. One of the metals that is being introduced is copper. Although few diffusion barriers materials effectively block the diffusion of copper, metal nitride, for example tungsten nitride, has been shown to act as good barriers against copper diffusion.
Tungsten Nitride (WN) films have been deposited in the past using reactive sputtering, chemical vapor deposition (CVD) from tungsten hexafluoride (WF6) and ammonia (NH3), and metal-organic CVD using tungsten hexacarbonyl W(CO)6 and NH3.